With the establishment of the concept that anterior pituitary hormone secretion is significantly controlled by hypothalamic neurohormones, it is unequivocally requisite to attempt to regulate the specific secretory activity of this gland for the purpose of controlling tumorigenesis. Thus, the objectives of this study are: 1. To define the hormonal environment prerequisite for the development and growth of carcinogen-induced leukemia in Long-Evans rats. 2. To determine the effect of drug-induced alterations of the activity of adrenergic, dopaminergic and serotoninergic pathways of the central nervous system on progression of carcinogen-induced leukemia in Long-Evans rats. 3. To demonstrate control of the growth of carcinogen-induced leukemia in Long-Evans rats by suppression of pituitary hormone secretion by administration of neuroendocrine influencing drugs.